Production method of layered sound absorptive non-woven fabric

ABSTRACT

Production method of layered sound absorptive non-woven fabric, which comprises a resonance membrane which is positioned between two layers of the card fibrous web, while both layers of the card fibrous web are produced simultaneously in carding machine, from which each layer of the card fibrous web is separately brought into the device for production of nanofibres through electrostatic spinning, in which to the side of at least one layer of the card fibrous web adjacent to the remaining layer of the card fibrous web a layer of nanofibres is applied, after then both layers of the card fibrous web near to one another until their adjacent sides sit down one on another, they are laid one on another in a selected quantity of layers and the layers join mutually.

TECHNICAL FIELD

The invention relates to the production method of layered soundabsorptive non-woven fabric, which comprises a resonance membrane formedby a layer of nanofibres having diameter to 600 nanometers and basisweight of 0,1 to 5 gm⁻², which is positioned between two layers of thecard fibrous web.

BACKGROUND ART

The CZ PV 2005-226 discloses a layered sound absorptive non-woven fabriccontaining a resonance membrane and at least one another layer offibrous material. The resonance membrane is formed by a layer ofnanofibres having diameter to 600 nanometers and basis weight of 0,1 to5 gm ⁻² and the resultant fabric is formed by a cross laying to therequired thickness and weight.

In an advantageous embodiment the layer of card fibrous web here formsthe bearing layer on which during electrostatic spinning the layer ofproduced nanofibres is being deposited, and consequently both layersjoin together in a known manner at the specified temperature in the hotair chamber.

To increase the efficiency, according to the mentioned document anotherlayer of card fibrous web may be applied on the fabric, namely from theoriginally disposable side of nanofibrous layer. Possibly there may beanother layer, the double or triple one.

Nevertheless the background art for such three- and more layered fabricrequires that at least one fibrous web is prepared separately and thesame after then is joined to the nanofibrous layer of already producedtwo-layer fabric. This complicates the production and makes it moreexpensive.

The goal of the invention is to eliminate the shortcomings of the knownsolutions or to restrict them considerably.

THE PRINCIPLE OF INVENTION

The goal of the invention has been reached by a production method oflayered sound absorptive non-woven fabric containing a resonancemembrane formed by a layer of nanofibres, which is positioned betweentwo layers of card fibrous web according to the invention, whoseprinciple consists in that, both layers of card fibrous web are producedsimultaneously in carding machine from which at least one layer of cardfibrous web is brought into the device for production of nanofibresthrough electrostatic spinning, in which to the side of this layer ofcard fibrous web adjacent to the remaining layer the layer of nanofibresis applied, after then after exiting the device for production ofnanofibres through electrostatic spinning, both layers of card fibrousweb near to one another until their adjacent parts, out of which atleast on one there is applied a layer of nanofibres forming theresonance membrane, touch one another.

From the point of view of spatial complexity and arrangement ofindividual elements of the device for production of nanofibres throughelectrostatic spinning it is advantageous if the layer of nanofibres isbeing applied only on one of layers of the card fibrous web, while thelower layer of card fibrous web also passes the device for production ofnanofibres through electrostatic spinning, nevertheless outside itsspinning compartment.

In case the structure of the device for production of nanofibres doesnot enable passage of a layer of card fibrous web on which the layer ofnanofibres is not applied outside the spinning compartment, this layeris guided totally outside the device for production of nanofibresthrough electrostatic spinning, and to the layer of card fibrous webpassing through the spinning compartment it is nearing only after thedevice for production of nanofibres through electrostatic spinning.

According to the claim 3 it is advantageous if both layers of cardfibrous web are guided separately into the device for production ofnanofibres through electrostatic spinning, while at least one layer ofthe card fibrous web passes through the spinning compartment of thisdevice and to the side of this layer of the card fibrous web adjacent tothe second layer the layer of nanofibres is applied.

Guiding of the second layer of the card fibrous web enables its passageoutside the spinning compartment of the device for production ofnanofibres through electrostatic spinning.

In embodiment according to the claim 5 both layers of the card fibrousweb are guided through the spinning compartment of the device forproduction of nanofibres through electrostatic spinning, in which one,the upper, layer of nanofibres is applied on the side of the first layerof the card fibrous web adjacent to the second layer of the card fibrousweb, and the second, the lower, layer of nanofibres is applied on theside of the second, the lower, layer of the card fibrous web reverse tothe first, the upper, layer of the card fibrous web. This embodimentachieves a higher sound absorption capacity as it contains two resonancemembranes formed by layers of nanofibres, while each of these membranesmay absorb a different range of sound waves.

Another increasing of absorption capacity may be achieved according tothe claim 6 by that, to the layer of nanofibres applied on the side oflower layer of the card fibrous web there is joined at least one anotherlayer of the card fibrous web with a layer of nanofibres applied on thereverse side of this another layer of the card fibrous web.

At the same time it is advantageous especially from the point of view ofcosts, if this further layer of the card fibrous web is produced on thesame carding machine as the upper and lower layer of the card fibrousweb.

Or it may be advantageous if this further layer of the card fibrous webis produced in another carding machine than the upper and lower layer ofthe card fibrous web. This embodiment is rather more expensive, but itallows adding of another one up to three further layers of the cardfibrous web.

Especially due to protection of lower layer of nanofibres it isadvantageous if to the layer of nanofibres applied on the outer side oflower layer of the card fibrous web reverse to the previous layer of thecard fibrous web an auxiliary layer of the card fibrous web is joined.

The auxiliary layer of the card fibrous web may be produced on the samecarding machine as the upper and lower layer of the card fibrous web oron another carding machine.

The advantage of another variant of solution according to the inventionconsists in that both layers of card fibrous web are guided through thespinning compartment of the device for production of nanofibres throughelectrostatic spinning, in which to the mutually adjacent sides of bothlayers of the card fibrous web there is applied always one layer ofnanofibres.

In this method it is possible to produce a layered fabric withcombination of nanofibrous layers of a different thickness, possibly ofa different nanofibrous material and so to reach a broader spectra ofthe sound being absorbed.

At the same time it is advantageous, if after exiting the device forproduction of nanofibres through electrostatic spinning the fabriccontaining at least two layers of the card fibrous web, in between ofwhich there is arranged at least one layer of nanofibres is formed bymeans of cross laying into layers.

Or according to the claim 14 the fabric containing at least two layersof the card fibrous web, in between of which there is arranged at leastone layer of nanofibres, after exiting the device for production ofnanofibres through electrostatic spinning may be guided into the layingdevice in which it is laid into layers.

In this manner it is possible to produce a continuous stripe of layeredfabric of a constant composition and specified thickness, which afterthen, as the need may be, is divided into panels of desired dimensions.

Further it is advantageous if layers of the fabric are mutually joinedby heating to the temperature of melting the material with the lowestmelting temperature, which is contained in layers of the fabric.

Through this method it is possible to choose between which layers of thefinal layered product the joint will be created by means of mutualsmelting of adjacent surfaces.

DESCRIPTION OF THE DRAWING

The embodiments of production lines for performance of the productionmethod according to the invention are schematically shown on thedrawing, where the

FIG. 1 represents the production line with passage of one card fibrousweb outside the device for production of nanofibres throughelectrostatic spinning, the

FIG. 2 a section of the production line with passage of both cardfibrous webs through the device for production of nanofibres throughelectrostatic spinning, while one of them is passing outside thespinning compartment, the

FIGS. 3 and 4 a section of the production line, in which the nanofibresare applied on both layers of the card fibrous web, while according tothe FIG. 3 after exiting the spinning device there is only one layer ofnanofibres between the two layers of card fibrous web, while accordingto the FIG. 4 there are after exiting the spinning device both layers ofnanofibres positioned together between the two layers of the cardfibrous web. The

FIG. 5 represents a section of the production line, in which the layersof nanofibres are applied on four layers of the card fibrous web and the

FIG. 6 a section of the production line according to the FIG. 3, atwhich on the carding machine simultaneously three layers of the cardfibrous web are being produced, while the third layer forms theauxiliary covering layer.

EXAMPLES OF EMBODIMENT

The FIG. 1 schematically represents the production line 1 forperformance of the production method of layered sound absorptivenon-woven fabric, known e.g. from the patent application CZ PV 2005-226,according to the invention.

At the beginning of the production line 1 there is arranged the knowncarding machine 2, which in a known manner prepares the upper layer 21of the card fibrous web and the lower layer 22 of the card fibrous webfor production of layered sound absorptive non-woven fabric. The layers21, 22 of the card fibrous web may be produced from staple bicomponentfibres of the type core-coating or of another suitable material.

After exiting from the carding machine the upper layer 21 of the cardfibrous web is guided into the device 3 for production of nanofibresthrough electrostatic spinning, which is for example the device forproduction of nanofibres through electrostatic spinning of polymersolutions according to the patent application CZ PV 2005-360. The lowerlayer 22 of the card fibrous web is guided outside the device 3 forproduction of nanofibres through electrostatic spinning.

The upper layer 21 of the card fibrous web in the device 3 forproduction of nanofibres is brought in between the pair of electrodesarranged in the spinning compartment 31 of the device 3 for productionof nanofibres through electrostatic spinning. After bringing the highvoltage of opposite polarity to these electrodes an electric field witha high intensity is created, which through its action of force to thepolymer solution in electrostatic field, e.g. on surface of one of theelectrodes from this polymer solution creates the polymer nanofibres.The created polymer nanofibres after their creation are deposited on thelower side of upper layer 21 of the card fibrous web and they create alayer 32 of nanofibres, which is adjacent to the lower layer 22 of thecard fibrous web.

After applying the layer 32 of polymer nanofibres of desired thicknessand/or desired basis weight, the upper layer 21 of the card fibrous webwith deposited layer 32 of nanofibres is exiting the device 3 forproduction of nanofibres through electrostatic spinning. The upper layer21 of the card fibrous web with deposited layer 32 of nanofibres isafter then brought to the lower layer 22 of the card fibrous web passingoutside the device 3 for production of nanofibres through electrostaticspinning and both layers 21, 22 are then together brought into the crosslaying device 4 positioned after the device 3 for production ofnanofibres. In the cross laying device 4 there is performed a knowncontinuous cross laying of layers 21, 22, which contain a layer 32 ofnanofibres, and the non-reinforced layered sound absorptive fabric 41 isproduced.

The non-reinforced layered sound absorptive fabric 41 is from the crosslaying device 4 brought into the hot-air chamber 5, where through theeffect of streaming hot air the upper layer 21 containing the cardfibrous web and the nanofibres are joined with the lower layer 22 of thecard web, and so the layered sound absorptive non-woven fabric 51 isproduced.

After the hot-air chamber 5 in the production line 1 there is arrangedthe cutting device 6, which from the sound absorptive non-woven fabric51 produces panels 61 of desired dimensions.

The cross laying device 4 may be replaced by any suitable laying device,which is able to lay the continuously brought layers 21, 22, whichcontain a layer 32 of nanofibres one on another and thus to produce thenon-reinforced layered sound absorptive fabric.

Variant of embodiment according to the invention, in which the lowerlayer 22 of the card fibrous web is guided through the device 3 forproduction of nanofibres through electrostatic spinning outside thespinning compartment 31 is represented in the FIG. 2. The device 3 forproduction of nanofibres through electrostatic spinning here forms acompact unit serving to guide also the lower layer 22 of the cardfibrous web.

In another variants of method according to the invention the layer ofnanofibres 30 is applied not only on the upper layer 21 of the cardfibrous web, but also on the lower layer 22 of the card fibrous web,possibly only on the lower layer 22 of the card fibrous web.

In the variant according to the invention represented in the FIG. 3 thedevice 3 for production of nanofibres through electrostatic spinningcomprises a spinning compartment 31, possibly two separated spinningcompartments 311, 312. Upon passage of upper and lower layer 21, 22 ofthe card fibrous web the nanofibres are here applied on lower surfacesof both layers 21, 22. When the layers 21, 22 comprising always the cardfibrous web and the layer 32 of nanofibres enter the cross laying device4, one layer 32 of nanofibres is to be found between the layers 21, 22of the card fibrous web and the second layer 32 of nanofibres is to befound on the lower surface of the lower layer 22.

Exemplary embodiment according to the FIG. 3 may be added by anotherlayers of the card fibrous web with applied layer of nanofibres. Inembodiment according to the FIG. 5 the device 3 for production ofnanofibres through electrostatic spinning of polymer solutions comprisesfour spinning compartments 311, 312, 313, 314, into which there arebrought four layers of the card fibrous web 21, 22, 23, 24 from twocarding machines. Upon passage of layers 21, 22, 23, 24 of the cardfibrous web the nanofibres are applied on the lower surface of layers21, 22, 23, 24. When the layers 21, 22, 23, 24 of the card fibrous webcontaining the layer 32 of nanofibres enter the laying device 40 thelayers 21, 22, 23, 24 are nearing one to another until their contactoccurs, while between the layers 21, 22, 23, 24 of the card fibrous webthere is always one layer 32 of nanofibres. On the bottom surface of thelower layer 22 of the card fibrous web there is also a layer of 32 ofnanofibres. By this layer 32 of nanofibres the lower layer 22 of thecard fibrous web is laid in the laying device on the upper layer 24 ofalready applied layers of the card fibrous web 21, 22, 23, 24. Thedisadvantage of this solution is a fact, that one of the outer layers ofthe resultant layered sound absorptive non-woven fabric 51 is the layer32 of nanofibres deposited on the utmost lower layer 22 of the cardfibrous web, which is a part of the layered sound absorptive non-wovenfabric 51. This problem is solved by exemplary embodiments according tothe FIGS. 4 and 6.

According to the FIG. 6 the carding machine 2 according to the FIG. 3provided by means for creation of three layers 21, 22, 25 of the cardfibrous web, out of which the layers 21, 22 are brought into thespinning compartments 311, 312 of the device 3 for production ofnanofibres through electrostatic spinning of polymer solutions, and thelayer 25 of the card fibrous web is guided outside the spinningcompartments or also outside the device 3 for spinning and to the layers21, 22 on which in the spinning compartments 311, 312 of the device 3for spinning there were applied layers 32 of nanofibres, it joins beforeentering or on entry into the laying device 40 and so it creates theauxiliary layer 25 of the card fibrous web serving for protection ofnanofibrous layer applied on the lower layer 22 of the card fibrous web.

Also the device according to the FIG. 5 may be provided by an auxiliarylayer 25.

Also in a variant represented in the FIG. 4 the device 3 for productionof nanofibres through electrostatic spinning comprises the spinningcompartment 31, possibly two separated spinning compartments 311, 312,as it is described at the embodiment according to the FIG. 3.Nevertheless the nanofibres are here applied on layers 21, 22 so thatthe applied layers 32 of nanofibres are positioned on mutually adjacentsurfaces of layers 21, 22 of the card fibrous web. The method ofapplication of nanofibres down from top on the upper surface of thecarrying layer is described e.g. in the CZ 294274. Here the polymersolution is filled into a closed vessel, out of which the polymersolution is brought to the surface of the charged electrode, while withthe polymer solution there is wetted e.g. the upper section ofcircumference of the cylinder, which from the vessel carries out on itscircumference the necessary quantity of polymer solution.

In all variants represented in the FIGS. 2 to 6 the production procedureof layered sound absorptive non-woven fabric 51, possibly of it createdpanels 61 proceeds in a manner shown in the first embodiment variant ofthe production line 1 according to the invention, while for the purposeof the invention it is not important which laying device 40 was applied.

It is obvious, that alternatives of embodiment of the production line 1enable to reach various inner arrangements of the sound absorptivenon-woven fabric 51 and to fulfil in a variable manner the requirementsas to properties of means absorbing the sound. Especially it is possibleto each layer 21, 22, 23, 24 of the card fibrous web to apply a layer 32of nanofibres of different properties, at the same time under thedifferent properties it is primarily understood the different material,out of which the nanofibres are produced, the different thickness of thelayer 32 of nanofibres, the different diameter and/or length ofnanofibres and other properties influencing absorbing of the sound.

The described examples of embodiment permit to create furthercombinations, which are not described in a detail as they are quiteobvious for an average specialist.

LIST OF REFERENTIAL MARKINGS

1 production line

2 carding machine

21 upper layer of the card fibrous web

22 lower layer of the card fibrous web

3 device for production of nanofibres through electrostatic spinning

31 spinning compartment

311 upper section of spinning compartment

312 lower section of spinning compartment

32 layer of nanofibres

4 cross laying device

41 non-reinforced layered sound absorptive fabric

5 hot-air chamber

51 layered sound absorptive non-woven fabric

6 cutting device

61 panel

1. Production method of layered sound absorptive non-woven fabric, whichcomprises a resonance membrane formed by a layer of nanofibres havingdiameter to 600 nanometers and basis weight of 0,1 to 5 gm ⁻², which ispositioned between two layers of the card fibrous web, wherein bothlayers of the card fibrous web are produced simultaneously in cardingmachine, from which at least one layer of the card fibrous web isbrought into the device for production of nanofibres throughelectrostatic spinning, in which to the side of this layer of the cardfibrous web adjacent to the remaining layer the layer of nanofibres isapplied, after then after exiting the device for production ofnanofibres through electrostatic spinning both layers of the cardfibrous web near one to another until their adjacent parts, out of whichat least on one there is applied a layer of nanofibres forming theresonance membrane, sit down one on another.
 2. The method according toclaim 1, wherein the lower layer of the card fibrous web is passingoutside the device for production of nanofibres through electrostaticspinning.
 3. The method according to claim 1, wherein both layers of thecard fibrous web are guided separately into the device for production ofnanofibres through electrostatic spinning, while at least the upperlayer of the card fibrous web is passing through the spinningcompartment of this device and to the side of this upper layer of thecard fibrous web adjacent to the lower layer the layer of nanofibres isapplied.
 4. The method according to claim 3, wherein the lower layer ofthe card fibrous web is passing outside the spinning compartment of thedevice for production of nanofibres through electrostatic spinning. 5.The method according to claim 1, wherein both layers of the card fibrousweb are guided through the spinning compartment of the device forproduction of nanofibres through electrostatic spinning, in which onelayer of nanofibres is applied to the side of the upper layer of thecard fibrous web adjacent to the lower layer of the card fibrous web andthe second layer of nanofibres is being applied to the side of lowerlayer of the card fibrous web reverse to the upper layer of the cardfibrous web.
 6. The method according to claim 5, wherein the layer ofnanofibres applied to the side of lower layer of the card fibrous webreverse to the first layer of the card fibrous web there is joined atleast one another layer of the card fibrous web with a layer ofnanofibres applied on the reverse side of this another layer of the cardfibrous web.
 7. The method according to claim 6, wherein further layerof the card fibrous web is produced on the same carding machine as theupper and lower layer of the card fibrous web.
 8. The method accordingto claim 6, wherein this further layer of the card fibrous web isproduced on another carding machine than the upper and lower layer ofthe card fibrous web.
 9. The method according to claim 5, wherein thelayer of nanofibres applied on outer side of lower layer of the cardfibrous web reverse to the previous layer of the card fibrous web anauxiliary layer of the card fibrous web is joined.
 10. The methodaccording to claim 9, wherein the auxiliary layer of the card fibrousweb is produced on the same carding machine as the upper and lower layerof the card fibrous web.
 11. The method according to claim 9, whereinthe auxiliary layer of the card fibrous web is produced on anothercarding machine than the upper and lower layer of the card fibrous web.12. The method according to claim 1, wherein both layers of the cardfibrous web are guided through the spinning compartment of the devicefor production of nanofibres through electrostatic spinning, in which tothe mutually adjacent sides of both layers of the card fibrous web thereis applied always one layer of nanofibres.
 13. The method according toclaim 1, wherein after exiting the device for production of nanofibresthrough electrostatic spinning the fabric containing at least two layersof the card fibrous web, in between of which there is arranged at leastone layer of nanofibres, is formed by means of cross laying into layers.14. The method according to claim 1, wherein after exiting the devicefor production of nanofibres through electrostatic spinning the fabriccontaining at least two layers of the card fibrous web, in between ofwhich there is arranged at least one layer of nanofibres, is guided intothe laying device in which it is laid into layers.
 15. The methodaccording to claim 1, wherein the layers of the fabric are mutuallyjoined by heating to the temperature of melting the material with thelowest melting temperature, which is contained in layers of the fabric.